Method of making seals for coaxial electron discharge devices



y 22, 1952 J. LYSAK 2,603,915

METHOD OF MAKING SEALS FOR COAXIAL ELECTRON DISCHARGE DEVICES Filed Aug.2'7, 1949 INVENTOR JOH N LYSAK Patented July 22, l952 METHOD OF MAKINGSEALS FOR COAXIAL, ELECTRON'DISCHARGE DEVICES John Lysak, Newark, N. Jassignor to Radio Corporation of America, a corporation of Delaware IApplication August 27,1949, Serial N 0.112,?32

Claims.

Th invention relates generally to methods of making seals and moreparticularly to a method of making seals between coaxial elements ofelectronv discharge devices.

Some types of electron discharge devices comprise coaxial elements andare useful at ultra high frequencies. One such device comprises a diodeemployed to detect noise factors in a circuit without impairing thenormal functions of endof the device, the sealing ring being first fixedto the inner member prior to the assembly of the device. Whil this typeof sealing ring has to some extent avoided the difiiculty characterizingthe use of a sealing ring. on-the outer member as described above, ithas not been completely satisfactory. The disposition of the entiresealing ring within the outer member has resulted in a shielding of thering from sealing the circuit. Such diodeis described and claimed firesemployed to fuse the ring to the outer memin Patent 2,506,644 issued toH. Johnson. One ber. This has necessitated the application of feature ofthe diode referred to is the provision more heat to the outer memberthan would be of a filamentary connector between elements of required ifthe fires could be applied directly to theinner coaxial member and whichextends latthe ring. As a consequence the heat quantity reerally of saidinner member to comprise a proquired for making a seal according to thisprior jection from the periphery of said member. Anp actice is ten sohigh as to damage the seal other feature involves the relative lengthsof the pr viously m d b ween h s al r n inner and outer membersof thecoaxial structure. he inner memb r- F r hermor h p r ion of The innermember islon'ger than the outer memhe inner e r extending o e s of herto provide for extensions of the inner memthe outer 'member are appreheated and ber from the ends of the outer member. These the softened assof the seali has a tendextensions are adapted to serve as contact memeyo creep along the inner du or and ball bers and it is desirable thatthey provide a maxiup thereon. The annular end surface between mum areaof surface contact. The inner and thetwo coaxial members that thesealing r outer members are usually fixed with respect to of this typeprovides-becomes deformed and reeach other by rings of insulatingmaterial filling u s t Surface are? of the P j c n P on restrictedannular spaces adjacent the ends of Of the inner member required for a d0011- the outer member. These rings serve to .close tthe ends of theouter member and to provide 9. Accordingly it is the object of theinvention to space therein that may be evacuated. I provide an improvedmethod of making a seal Several difficulties characterize themanufacbetWeen relatively s v p d OOeXlal emture of a device of the typedescribed. These e sdifficulties are centered in the seal effected be- Afurther object is to p de a s a m od tween the inner and outer member bythe lusing sub-assemblies for the inner and outer ing rings referred to.Some types ofseals heremembers of a coaxial device wherein the outertofore used involve application of a sealing ring member is free fromobstruction on its inner sur-= of insulating material to both the innerand outface to facilitate assembling of e de ce. er members in view ofthe ease with which the h r object s t v e a impr ved two bodies ofsealing material may subsequently method f r making settle at d p ionsof a be fused to form a seal. However, the presence coaxial devicebetween relatively closely spaced of a sealing ring on 'theouter memberrenders eoaXi'al members Without impairing o 0011- insertion of theinner l membe'r. therein difficult Fling characteristics of i end prtionsbecause of the care-requiredlto prevent damage A f r Object is top vi a method for to the filamentary connector referred to. A makingfiat surfaced seals between a fiat ended further disadvantage of thispractice has been 5 coaxial device having two coaxial and relatively thelack of uniformity in the amount of insuclosely spa d members jo d y aidseals. lating material used.- This-lack of' uniformity Another Object isto provide a method of makhas resulted from the-fact that the priorpracing a glass-to-metal seal between two relatively tice describedrequired hand glass blower techclosely spaced coaxial metal members andan inniques. This lack of uniformity has heretofore termediate bodyof-insulating material, wherein resulted in variations in the seals withconsequent a surface of said insulating body extending from variationsin the electrical characteristics of the one to the other'of said metalmembers is subdevices in which they are used. v, stantially fiat. v i

f Other types of sealsheretofore usedinvolve A further objectis toprovide amethod of the a plication of'asingle sealing ring at, each 55,sealing aglass beaded metallic member to an- 3 other metallic memberwithout disturbing the seal of the glass bead to the first-namedmetallic member.

Another object is to provide a method of forming uniform seals in aplurality of devices having relatively closely spaced members.

A further object is to provide a novel method of forming asealing ringfor use, between two coaxial members.

Another object is to .provide an advantageous method of making anelectron discharge device.

According to the invention the foregoing dif.-. ficulties are overcomeand the objects-referred to are realized by the use of a sealing ring ofnovel shape and predetermined diameter. I The sealing ring is providedwith an end surface that is flat adjacent its inner edge and that-tapersadjacent.

the periphery of the ring, the taper providing an annular mass ofinsulating material. The sealing ring is first sealed to the innermem-berand i of a. diame er. that s. S h e s a the nner. ia Dime-out mmbe o "ease in assembling; the; members.- When the inner and outermembers of the device are assembled for sealing, the tapered; portion ofthe ring extends be nd he end h uter m ber nd the a portion oftheringsurfacereferred-tois substantially coplanar with respect toanend oftheouter member. This sealing; ring and the manner of 'disposingit. areadvantageous in several respects. The extending taperedportion of thesealing ring is directlyaccessible tothesealing fires to-thereby reducethe heat quantity'required for a seal with consequent preservation. ofthe previously made seal-between the ring and the inner member. Auniform mass-of sealing; -material is; used in each ring asa consequenceofa novel method offorming the rings. A. reservoin of sealing: materialis provided so that the diameter of'the-ring may besubstantiallylessthan: that of the inner portion of the. outer member,for easev in. assembling. the members. Displacement of; the taperedportion of. the ringfrom theinner edge of the sealing ring prevents aballing up. of the sealing material 'on the inner membentherebycontributing to the preservationof a desirably large. contact, surface,on the "mner member.

Further objects and advantages of the inventicn willbecome evident asthe present description continues.

Referring to the drawing:

Figure 1 is a longitudinal sectional view of a coaxiaidevice in whichthe. practice of my invention is. particularly advantageous;

Figure 2 shows a side View partly insectionxof the inner member ofv thecoaxial deviceo-f Fig-. ure 1; i

Figure 3 depicts the initial step: in sealing the members of the coaxialdevice of. Figure 1';

Figure 4. shows the finalstepin.app1icant.s novel sealing method;

Figure 5 illustrates one Way in whichthenovel insulating ring or bead onthe inner member may be formed.

Referring to Figure Lthere isshownan electrical device comprising a twoelement vacuum tube forming a section A of a coaxial transmission line.The section A comprises a cylindrical outer conductor Wanda cylindricalinner conductor I l, the latter carrying'a cathode filament I3. In orderto fix the desired; coaxial arrangement between the conductorsor membersreferred to, insulatingrings l4; which maybe of glass are sealed betweenend iportionsof the outer conductor I0 and the innermember comprisinginner. conductor- II and an. elongated:

. at ultra high frequencies, a diode of the type described isadvantageous since it may be inserted into ultra high frequency coaxialline circuits without afiecting the circuit. One importantconsideration. in associating the noise diode in a circuit tobe testedis the coupling between the diode and the circuit. This coupling shouldinvolve maximum surface contact. The nature of the end surfaces of therings I4, l5 materially aiiect the amount of surface engagementpermitted between the diode and. the circuit contac lements. Thus, ifthe sealing material which may be glass, balls up. around; the innerconductor of the diode so as to extend appreciably. beyond. the. endsofthe. outer conductor Ill, it. serves effectively-- to stopcompleteinsertion of the. diode intoa circuit element, thereby reducing the'areaof.v surface contact therebetweem Such. reduced. areaof surface contactmay introduce. impedance effects to the circuit of a disturbingcharacter and thereby render noise. measurements inaccurate. If theouter end surfaces of. the. rings. [-4, l5j-are flat and substantiallycoplanar with the endsof theouter conductor [0' a maximum area. of.surface. contact is provided. which avoids. distmbance. of; the-ciru tbeing. t st d. andjcontributes to; accurate measurements.

In accordance with themethodof the. invention, aelass ringofr ovellcon iuration is sealed o ach r r n ofgthe nner. member Ifl I'd-as shown inFigure 2 Sealing; rings Ma, and; [5a, w h ma b o l ss, are rq ii edwithtap ring peripheries l8, IQ and have a. diameter slightly less thanthe inner diameter ofl'the outer, member 10.

B t r h se. i t resy i hesea neringsare significant. The reducemdiameterof the sealing in s Permits n. a passa e oijthe inner. m m bers l I,lfi'into the outerm emberl flg The tapered perip e. eal n prov desares.-ervoir of sealing material for filling the. Spaces wee e ea in s. anthe; inner wa iof. the'outer member I0. The displacementqfjthe taperedportion of" the rings from .t h e inner, members I I rev nts 11 1 5 11.qf heifi alrs m ia e n e member. referred. i rmer h taper thesealinains. quires arelatively ma ea j uantityifor nsine. and comp e et e sealsfisrres vesthe seals v ou l de. etw h sealin rings. an the; innermembers. ll, lfig This. reducedheat.

quanti d: r at v y sma l porti n. r the.

mass of the sealingrin'gs that' is fused thereby.

rv p s rve un erm r. insealsade n several different devices; of the typedescribed;

- This-uniformity-in seals is -alsoaccornplished;as a.

result ofjthemethodofforming-the sealing rings.

This method is shown in; Figure; fiipwherein,

that .a downward movement of upper member 2.0 of theforming'tool towardsthe lower member 2| will result in shaping the sealing ring inconformity'with, the. shaping surfaces of the forming tool. The shapingsurfaces on the upper member; '28 are such as to provide a rightcylindrical end portion of the sealing ring and the shaping; surfaces ofthe lowermember provide anannular taper rising outwardly to theperiphery of the sealing ring. I

The sealing of a ring of insulating material to each endportion of theinner members I I, I6 and forming the ringsas shown in Figure 5, resultsin-a,sub+asse mbly asshown in Figure 2.

assembly at positions where the outer surfaces 22, 23 of the rings arespaced from each other a distance equal to the length of the outermember l0, so that when the inner assembly is disposed within the outermember in proper position for sealing the rings to the latter, each endof the outer member is coplanar with one of the surfaces 22, 23 on thesealing rings Ma, l5a.

After the sealing rings Ma; l5a are sealed to the inner member asindicated above the device is assembled by inserting the inner memberinto the outer member with the surfaces 22, 23 coplanar with the ends ofthe outer member. The two members are held in this position as shown inFigure 3 by suitable supports 24, 25. It will the inner conductor. As aconsequence a contact member adapted to engage the portion 29 willsealing of one, ring to the inner member of the The sealing of theinsulating rings tothe inner assemblv l l, l6'may be accomplished priorto the assembly of the inner member in the outer membe noted that inthis position the taper l9 extends beyond an end of outer member It.

The burners 2B, '21 are disposed to play a flame that is substantiallyrestricted to the outer cylindrical surface of the taper [9. The heatingefiect of the flame is therefore restricted to the tapered material andas a consequence the tapered material melts and fills the space 28between the sealing ring and the outer member ID. It will be noted thatduring the application of the flames to the sealing ring in thisposition the portion 29 of the inner member is shielded from the flameand consequently remains substantially cool. If therefore any of themolten sealing material should travel towards the inner member, thematerial would not ball up on this member in view of its relativecoolness. However, due to the tapered shape of the end surface of thesealing ring the molten sealing material would fall by gravity into thespace 28 and be blocked from reaching portion 29 of the inner member bylower unmelted portions of the taper I9.

In view of the concentration of the flames on the tapered portion of theinsulating ring, the

outer member I0 is relatively cool and may render it therefore difiicultfor the molten sealing material to adhere thereto sufliciently well fora good seal. Accordingly, the burners are subsequently lowered to aposition where the flames play upon the end portion of member Ill asshown in Figure 4. This heats the Wall of the member l0 so as to bewetted by the sealing material for the formation of a good seal.

It will be noted in Figure 4 that the ultimate shape of the sealing ring[4 includes flat surface 30 substantially coplanar with the end of outermember l0. Furthermore the surface 30 forms a clean-cut right angle withthe portion 2 9 of device it will be apparent that anothering is formedand sealed to the other end of the member in like manner. 7. Y v

It will thus be apparent that the device of the invention and the methodof making it are characterized by many advantagesabsent in prior'arttechniques. Thusthe manner of forming the sealing rings assures of anaccurate control of the amount of sealing material in each ringcontributing to uniformity in seals and good operation of the device.The formation'of a taper in the sealing rings permits a control over thesealing operation whereby. the finished seal is provided with a flatsurface normal to a contact member for preserving a relatively largecontact area on the device. This flat surface results automatically Whenthe seal ismade in accordance with the invention and requires no formingtool. Furthermore the control afforded by my novel method assures a goodseal without harm to previously made seals. In addition, the taper.permits a spacing of the sealing ring from the inner walls of the outermember and. has the advantage of facilitating insertion of the innermember into the outer member for expediting assembly of the device.

While my invention is particularly useful in relatively small sizeddevices in which it is extremely difiicult to make a seal betweencoaxial members and preserve a flatness at the end portions of thedevice, it may also find application in larger devices. Furthermore theinvention may be used in instances where the outer member is made of anon-metallic substance such for example as glass. Accordingly theinvention is not to be regarded as limited to the precise embodimentdescribed but is to be given a scope commensurate with the appendedclaims.

I claim:

1. Method of assembling an electron discharge device having coaxialmembers, comprising sealing a ring of insulating material on the innermember, forming a taper in one end surface of said ring rising from anintermediate portion of said surface toward the periphery of said ring,extending the inner member with said ring into the outer member, withsaid taper extending beyond an end of the outer member, heating saidtaper only to melt it and heating an end portion of said outer memberfor forming a flat surfaced seal between said ring and said outermember.

2. Method of assembling an electron discharge device having coaxialmembers, comprising forming a sealing ring of insulating material of adiameter less than the internal diameter of the outer member, providinga taper in one end surface of said ring, fixing said ring to the innermember, extending the inner member into the outer member with said taperextending beyond an end of the outer member to provide a free spacebetween the members, supporting said ring and said outer member againstrelative movement, heating the material forming said taper while sosupported to cause it to melt and flow into the free space between thering and the outer member, and heating the outer member to cause a sealbetween said ring and said outer member, whereby said end surface ofsaid ring is substantially flat for good contact purposes.

".3. Method of mounting two :eoaxial members "and sealing'theends'ofithe outer-ofsaid members. comprising sealing ;rings*o'fiinsulating materialiat spaced portions of the inner member, forming asaid rings to :provide a diameter thereof less than the inner diameterof :the outer member '..-and :to

:provide a taper inxthe outer :end'surfaces of-said rings,extending theinner member into :the :outer member with said tapers extendingffrom theends of the outer :member, said rings and said outer member formingannular :spaoes thereb'etween, 'heating :said :tapers only to 'melt thematerial thereof to causethe sameto' fiowinto said-annular .spaces, and:heating :portions of said outer mem- ;axial members comprisingproviding a sealing ring J on the inner member, vforming said sealingring to provide -a :taper in one surface thereof, said taper risingtowards the'periph'ery :of said ring,

and to provide a:diameter of said :ring less than the internal diameter:of :the I outer member. 'extending said innermember -into the outermember with said taper extending beyond amend or "said .outer'member andwitho'said ring spaced-from the vinner'walls of the outer member to form-an' annular space therebetweemheating said-taper only to cause thematerial .thereof to melt and flow into said annular space, and heatingsaidouter 8 Zmem'ber :to pause said "material seal thereto, whereby saidsurface ot-said :ring is substantially -flat forigoodlcontact purposes.

5. Method of forming :a seal between two ooaxial members eomprising:fi-xing' :a sealing ring to the innermeniber, supporting said sealing:ring within the outer :member, @witha portion of said ring extendingbeyond one end of said :outer member, said ring being spaced from the=outer member to provide an annular space therbetween, 'heating 'saidportiononl-y of said ring to cause it to melt and flow into said annularspace and heating said outer member ito cause the anoiten portionxto wetaportion:ofwsaid outepmember for efieotinga sealitherewith, wherebysa'idzmolten material i ifree to travel :inxa direction. away from theinner member to prevent :a balling up of the materialon said inner'member.

REFERENCES EGITED 'The followingxre'ferences are of record in the fileof "this patent:

UNITED -SPATES RATENTS Number Name Date 2,121,600 Knowles et a1June*'21,"l 9'3'8 2,125,315 1 'Ronoi Aug. '2, 1938 2,174,375 Beggs "Sept.'26,'1939 2,296330'7 Power Sept. 22, I942 23341 ,920 -Hull JFe'b. 15,1944

